[The role of small hydraulic engineering installations in altering the habitat conditions for mollusks--the prime intermediate hosts of Opisthorchis].

The small hydrotechnique objects, such as irrigation and drainage systems, fish cultivating ponds, isolate and cascade artificial water reservoirs, channels considerably change the ecological conditions of mollusks of the genus Codiella, the first intermediate host of Opisthorchis felineus. Some of these engineering objects engross the mollusks's population. The others are unfavourable for its existence.